Projectile fuze

ABSTRACT

Fuze including safety element ( 30 ) includes an acceleration detector ( 31 ) that acts on a timer ( 32 ) coacting with a primer housing rotor ( 14 ). Rotation of the rotor can be halted by a second safety device ( 35 ) responsive to the dynamic pressure generated by the speed of the projectile ( 11 ) in flight. For this purpose, the device includes a diaphragm ( 36 ) engaging a flexible blade ( 51 ) to space apart the end ( 55 ) of the blade and the rotor when the dynamic pressure has a predetermined value, whereby a primer ( 18 ) can be moved into line in the explosive train. When the dynamic pressure is too low, the end ( 55 ) stops the rotor ( 14 ) from rotating and the firing procedure is also blocked in a notch in the rotor ( 14 ). The resulting fuze thus has highly reliable dual safety element responsive to two separate physical phenomena and having a simple construction.

The present invention concerns a missile fuse with an ignition device and security means intended to enable ignition of the missile only under predetermined conditions.

Fuses of this type are known, for instance, as described in the patent CH 650.330. The security means of these fuses generally comprise an acceleration detector cooperating with a delay device.

It is the aim of the present invention to create a fuse having a still higher ignition security, a highly reliable function, simple design, and containing a small number of components.

To this end, the fuse according to the invention is characterised in that the security means comprise a detection device that is sensitive to the dynamic air pressure arising at the missile in flight, and that is designed so as to enable ignition of the missile when this dynamic pressure attains a predetermined value of dynamic presssure corresponding to a given speed of the missile, but to prevent ignition of the missile when the dynamic pressure does not attain this predetermined pressure value.

The dynamic pressure created by the missile in flight constitutes an additional criterion of security which allows all risks of undesired ignition to be eliminated. Such a device moreover yields a very high security and reliability while keeping a simple design with a small number of components.

Advantageously, said detection device comprises a detector element able to be at least partially displaced and/or deformed under the influence of the dynamic air pressure, so as to enable ignition when the dynamic pressure attains the predetermined value, or prevent ignition in the opposite case.

A particularly reliable function is secured by these features.

Advantageously, said detector element is able to occupy a rest position as well as an ignition position when said value of the dynamic pressure is attained, and the security means are arranged so as to definitively prevent the detector element from taking up the ignition position when the value of dynamic pressure is not attained after a predetermined period of time counted from missile launch.

The security of the fuse thus is still further enhanced by the fact that the ignition mechanism is definitely blocked when the predetermined speed is not attained within a given period of time.

In a preferred embodiment, the detector element is housed in a chamber of the fuse that is linked by a channel terminating in a hole situated in the front section of the fuse, and comprises a transmission element that can enable ignition or interrupt the ignition process.

The dynamic pressure detection device thus is well protected against all deterioration prior to or during the flight.

Highly favourably, said detector element comprises an elastic membrane retained at its borders in said chamber that can curve in under the dynamic pressure, this membrane then acting on said transmission element constituted by a flexible blade so as to deform and/or deplace it, thus allowing ignition to occur.

This design is particularly simple and reliable, and allows a fuse of doubled security and a very modest cost price to be obtained.

Further advantages will become evident from the characteristics expressed in the dependent claims and from the description in which hereinafter the invention will be set forth in greater detail with the aid of drawings representing schematically and in exemplary manner an embodiment.

FIGS. 1A, 2A und 3A represent the fuse in partial section in three different positions.

FIGS. 1B, 2B and 3B are plan views of the detonator rotor in the three different positions.

Referring to FIGS. 1A to 3A, the fuse 10 with its outer contours sketched in dash-dotted lines in FIG. 3A is intended to be mounted to the front section of a missile 11 by all adequate means, favourably with screws. Like all fuses, it comprises an ignition device 12 of which only a part is represented which is mounted rotatably in the form of a detonator rotor 14 on a shaft 16 that is integral with the body of the fuse. This rotor 14 comprises detonators 18, 19 that can be aligned by rotation of the rotor with a pyrotechnic chain (not illustrated) which in known fashion for instance includes a detonator intended to communicate the ignition to the missile's explosive charge.

The rotor can be set in rotation by a spring 15 so as to be shifted from an initial security position (FIG. 1B) to one of the ignition positions (FIG. 3B) in which one of the instantaneous or retard detonators 18, 19 is aligned within the pyrotechnic chain, depending on the position of a selector rod 22 cooperating with a peripheral cam 21.

The fuse comprises a series of security means 30 including amongst others at least an acceleration detector 31 designed to block the ignition device 12 when the acceleration of missile 11 is below a predetermined value, and to release the ignition device and initiate the ignition procedure when the acceleration is equal to or higher than this predetermined value.

This acceleration detector cooperates with a delay device 32 which in turn releases the rotor 14 after a predetermined period of delay so that it starts turning under the action of its spring.

The general design of the fuse with respect to the ignition device 12, the acceleration detector 31, the delay device 32 and the rotor 14 could for example be of the type described in Swiss patent No. 650.330 the text of which is an integral part of the present application.

Apart from the acceleration detector, at least a second security device 35 which is sensitive to another discriminating physical phenomenon, viz., the dynamic air pressure due to the missile in flight is contained in the security means 30; it is designed so that ignition will be enabled only when the dynamic pressure attains a predetermined value corresponding to a given speed of the missile, and will be prevented in the opposite case.

This second security device 35 comprises a membrane made of elastic material 36, for instance of plastic, which is housed in a chamber 37. The borders of the membrane are retained by the walls of chamber 37 by being sandwiched between an upper part 38 and a lower part 39 of the body 17. A channel 40 links a hole 41 located in the front section 42 of the fuse to chamber 37. This channel 40 has a first section 45 with a cross section smaller than that of a second section 46 located further back. In the state of rest the first section 45 of channel 40 is entirely closed off by a plug 47. When the missile is in flight, the dynamic pressure exerted by the air displaces the plug backwards into the second section 46 and thus opens channel 40 so that the membrane 36 is subject to the dynamic pressure of the missile in flight.

The lower part 48 of chamber 37 is rounded and linked to a ventilation channel 49. The security device 35 moreover contains a transmission element 50 intended to act upon the rotor as a function of the dynamic pressure.

This organ consists of a flexible metal blade 51 mounted on the lower part 39. A terminal section 54 of this blade 51 is inserted and held between parts 38 and 39, and is situated beneath the membrane 36. Blade 51 then follows part 39 and extends to a terminal portion 55 in the direction of rotor 14 in order to cooperate with cam 21 provided at the rotor's periphery.

This cam 21 has a recessed part 60 (FIGS. 1A and 1B) that allows the rotor 14 to rotate when the delay device has released it. It also has a stop part 61 (FIGS. 2A and 2B) with a first stop 62 that is arranged to stop the rotation of rotor 14 when the terminal portion 55 of blade 51 has not been lifted, and a second stop 63 intended to retain the flexible blade 51 in its low position within a notch 64 formed by the first and second stop.

The fuse functions as follows. Prior to the missile's launch, the mobile elements of the fuse are at their rest positions shown in FIGS. 1A and 1B. After launch the plug 47 rapidly retreats to open the air channel 40 so that a dynamic air pressure is established in chamber 37. Membrane 36 and section 54 of blade 51 curve downwards when this dynamic pressure attains a sufficiently high predetermined value, for instance 3 bars. The flexible blade 51 then forms a loop 66 curving upwards in its central section (FIG. 3A), and its lower end 55 is lifted above the level of the stop part 61.

Under the assumption that the missile's acceleration has a sufficiently high predetermined value, for instance 2500 g, the acceleration detector 31 is activated so as to start the delay device 32 which after a predetermined period of time releases the rotation of rotor 14. The rotor is not stopped by the blade 51 that is lifted above the stop part 61, and rotates by a predetermined angle so as to place one of the detonators 18, 19 into the pyrotechnic chain.

When the missile's speed is too low and the dynamic pressure does not attain a sufficiently high value, and is for instance less than 3 bars, while the fuse's acceleration has been larger than the predetermined minimum value, then rotor 14 is set in rotation, but its rotation is stopped by the stop part 61, FIGS. 2A and 2B. Moreover, terminal portion 55 is blocked in notch 64 under the action of spring 15 of the rotor 14. The ignition device thus is stopped and definitively blocked, none of the detonators 18, 19 is aligned with the pyrotechnic chain.

Thus, apart from the acceleration detector or detectors, the security means comprise at least one further security device sensitive to a further discriminating factor, which here is the dynamic pressure due to the missile's speed in flight. This dynamic pressure acts first of all on plug 47, which thus constitutes a first security element, and then on the security device 35 with its control blade 51. Ignition security thus is at least doubled while a simple and reliable design including few components is offered.

It is to be understood that the embodiment described hereinabove is in no way limiting and may receive all desirable modifications within the scope defined by claim 1. The security means more particularly could include still further elements, for instance elements sensitive to rotation in the case of gyrating missiles. In a simplified version the acceleration detector could be suppressed. The configuration of channel 40 and chamber 37 could be very different. Instead of a membrane 36, one could provide any other detector element for the dynamic pressure that can be at least partially displaced and/or deformed under the influence of the dynamic pressure, such as a valve urged against a rest position by a spring, or a braked airwheel set in rotation by the air under dynamic pressure. The detector element could cooperate with any mechanical or electrical component of the pyrotechnic chain. In the case of an electric fuse, it could for instance short-circuit the ignition charge when the missile's speed is insufficient. It could equally well act upon the delay device by releasing it only under predetermined conditions of the dynamic pressure. 

1. Missile fuse comprising an ignition device (12) and security means (30) intended to enable ignition of the missile only under predetermined conditions, characterised in that the security means contain a detection device (35) that is sensitive to the dynamic air pressure arising at the missile (11) in flight, and that is designed so as to enable ignition of the missile when this dynamic pressure attains a predetermined value of dynamic pressure corresponding to a given speed of the missile, but to prevent ignition of the missile when the dynamic pressure does not attain this predetermined pressure value
 2. Fuse according to claim 1, characterised in that said detection device (35) comprises a detector element (36) able to be at least partially displaced and/or deformed under the influence of the dynamic air pressure, so as to enable ignition when the dynamic pressure attains the predetermined value, or prevent ignition in the opposite case.
 3. Fuse according to claim 2, characterised in that said detector element (36, 50) is able to occupy a rest position as well as an ignition position when said value of the dynamic pressure is attained, and in that the security means (30) are arranged so as to definitively prevent the detector element (36, 50) from taking up the ignition position when the value of dynamic pressure is not attained after a predetermined period of time counted from missile launch.
 4. Fuse according to claim 2, characterised in that said detector element (36) is housed in a chamber (37) of the fuse that is linked by a channel (40) to a hole (41) situated in the front section (42) of the fuse, and in that it comprises a transmission element (50) that can enable ignition or interrupt the ignition process.
 5. Fuse according to claim 4, characterised in that the detector element comprises an elastic membrane (36, 50) that is retained at its borders in said chamber (37) and can curve in under the dynamic pressure, this membrane acting on said transmission element (50) constituted by a flexible blade (51) so as to deform and/or deplace it and thus allowing ignition to occur.
 6. Fuse according to claim 2, characterised in that the detector element (36, 50) cooperates with a mobile mechanical element (14) that can be displaced from an initial position to at least one ignition position after launch of the missile, the detector element (36, 50) being arranged so as to prevent the mobile mechanical element from being displaced to the ignition position when the value of dynamic pressure is not attained, and so as to move away from the mobile mechanical element so that this element may attain the ignition position when the value of dynamic pressure is attained.
 7. Fuse according to claim 6, characterised in that the mobile mechanical element consists of a detonator rotor (14) the periphery of which cooperates with a section (55) of the flexible blade (51), and in that this periphery comprises a first retaining element (62) preventing rotation of the rotor to the ignition position when the section of the flexible blade (51) has not moved sufficiently far away, and a second retaining element (63, 64) that is arranged so as to prevent the flexible blade (51) from moving away when the rotation of rotor (14) has been stopped by the flexible blade (51).
 8. Fuse according to claim 1, characterised in that it comprises at least one acceleration detector (31) arranged so as to enable or prevent the ignition procedure, depending on whether the missile's acceleration has attained a predetermined value or not.
 9. Fuse according to claim 7, characterised in that the acceleration detector (31) cooperates with a delay element (32) arranged so as to control the ignition procedure and the rotation of the detonator rotor (14).
 10. Fuse according to claim 4, characterised in that it comprises a plug (47) housed in its rest position in a first section (45) of said channel (40) which is closed off by it, and able to be displaced by the dynamic pressure to a second section (46) of the channel which is not closed off by it.
 11. Fuse according to claim 3, characterised in that said detector element (36) is housed in a chamber (37) of the fuse that is linked by a channel (40) to a hole (41) situated in the front section (42) of the fuse, and in that it comprises a transmission element (50) that can enable ignition or interrupt the ignition process.
 12. Fuse according to claim 3, characterised in that the detector element (36, 50) cooperates with a mobile mechanical element (14) that can be displaced from an initial position to at least one ignition position after launch of the missile, the detector element (36, 50) being arranged so as to prevent the mobile mechanical element from being displaced to the ignition position when the value of dynamic pressure is not attained, and so as to move away from the mobile mechanical element so that this element may attain the ignition position when the value of dynamic pressure is attained.
 13. Fuse according to claim 4, characterised in that the detector element (36, 50) cooperates with a mobile mechanical element (14) that can be displaced from an initial position to at least one ignition position after launch of the missile, the detector element (36, 50) being arranged so as to prevent the mobile mechanical element from being displaced to the ignition position when the value of dynamic pressure is not attained, and so as to move away from the mobile mechanical element so that this element may attain the ignition position when the value of dynamic pressure is attained.
 14. Fuse according to claim 5, characterised in that the detector element (36, 50) cooperates with a mobile mechanical element (14) that can be displaced from an initial position to at least one ignition position after launch of the missile, the detector element (36, 50) being arranged so as to prevent the mobile mechanical element from being displaced to the ignition position when the value of dynamic pressure is not attained, and so as to move away from the mobile mechanical element so that this element may attain the ignition position when the value of dynamic pressure is attained.
 15. Fuse according to claim 8, characterised in that the acceleration detector (31) cooperates with a delay element (32) arranged so as to control the ignition procedure and the rotation of the detonator rotor (14). 